Some knot sites state the two are the same. fintalk.com states they are not the same. Their duncan's loop doesn't slip after adjusting loop size. Does anyone know wich is correct. Does anyone use the fintalk duncan's loop?
Green

I learned the Duncan Loop years ago from Dave Whitlock's classic video "Fly Fishing for Bass". That version does indeed slip; you adjust a little loop for hte fly to swing freely, but when you set the hook the knot colapses onto the hok eye. After retrieving the fish, you open the loop and fish again.

I've seen diagrams of the Uni Knot and they look just like the knot I've always called the Duncan Loop.

The illustraion posted above looks kind of wierd; the loops in picture 3 have the wraps all through themain loop, but picture 4 looks like the loop to which the fly is attached somehow goes between some of the wraps. If so, I can see that this knot wouldn't slip. I've never seen any other illustrations of the Duncan loop looking like this.

As I understand it, the Duncan loop has the loop on the main line side, while the Uni-knot has the loop on the tag end side. Both slip down to the hook eye, and are great knots IMHO. All I know is that I use the Uni-knot for everything, and use two in place of a blood knot. Check all the uses on the link below, towards the bottom of the page.

Correct Duncan Loop:
There are many web-sites that describe and illustrate a fishing knot that is variously known as a Duncan Loop, Uni-Knot or Grinner.
In Geoff Wilson's “Complete Book of Fishing Knots & Rigs” the illustration of the “Duncan Loop” is shown improperly since the initial loop is formed on the standing line side of the hook eye.
This improper illustration of the Duncan loop is a non-slip loop that does not have similar strength as the Duncan loop and to my knowledge has no name.
When the initial loop is formed in the tag end portion of the line after passing through the hook eye it can form a proper Duncan Loop.
The illustration immediately below labeled “Uni-Knot” is a proper illustration of the Duncan Loop although the snugging and final setting are not shown. The Uni-Knot is a later renamed copy of the original Duncan Loop.
If pulled down and set properly the final configuration of the Duncan Loop, Uni-Knot or Grinner are all the same.

I believe that some of the confusion lies in the manner of which these knots are pulled down after the last wrap with the tag end is passed through the initial loop. In my knot and the Uni the tag end is pulled in the same direction as the standing line with sufficient force to allow the wraps to wind back over themselves to form a neat spiral over the standing and tag lines like a nail knot tied back over on the line itself. If this is not done the knot will not fold over and therefore form knots that differ in their final configuration and strength.

Here is a description of the history of the Duncan loop as described by Norman Duncan who came up with it in 1962. Vic Dunaway of the Miami Herald learned the knot, and began publicising it as the uni knot whereas in the Keys and SE coast of Florida it had already been known as 'Duncan's Loop' and later "A Duncan Loop" after its inventor.

One reason I have heard attributed to Dunaway was that he claimed to be the one who first used Duncan loops for connecting lines together by using two Duncan Loops in the manner of jam knots instead of the traditional blood knot.

In any event, I call them Duncan Loops out of respect for the originator. They are both the same knot when tied properly and neither is the unknown knot pictured in that link as Nedun has already said.

Some knots can be tied using different methods yet come out the same in the end. Two that come to mind are tying perfection loops to hook eyes and snelling hooks. Here is the method of snelling that I usually use, though the U-tube methods accomplish the same thing in the end. It is like a manual whip finish on a fly head without using that special tool.

Incidentally, a much easier way to tie a nail knot is not tying over a nail or a tube , but tying over a bent section of leader wire. Then you shove the tag through the leader wire loop and pull it back under the wraps. I still like that way better than the little metal tools.